Generally, valve trains in internal combustion engines (referred also to as engines) employ a valve lifter to transmit motion from a rotating cam lobe to one or more valves of the engines. During engine operations, for example, a valve lifter translates along a longitudinal axis, converting a rotary motion of the cam lobe into a reciprocatory action of the one or more valves, thereby facilitating an opening and a closure of the one or more valves, for engine operation.
Although operations of a valve lifter are commonly limited to a transition along the longitudinal axis during translatory motions, in some circumstances, a valve lifter may also undesirably turn about the longitudinal axis. Because of such turning (or rotation), an alignment between one or more components of the valve train may be altered. For example, a roller of the valve lifter, which may interact with the cam lobe, may move out of alignment with respect to the cam lobe, causing an incorrect engagement between the roller and the cam lobe. Such incorrect alignment/engagement may lead to an increased friction between the roller and the cam lobe, in turn causing an increased vulnerability of roller wear (and/or cam lobe wear), and thus, potential valve train failures.
U.S. Pat. No. 3,668,945 ('945 reference) discloses a guard that prevents roller tappets of a fuel injection pump from turning about their axes, during operation. The roller tappets are provided with flattened portions that cooperate with flattened parts of a securing pin to prevent the roller tappets from rotation.